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Monitoring Hemlock Forest Health in New Jersey Using Landsat TM Data and Change Detection Techniques

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Defoliation of eastern hemlock (Tsuga canadensis Carriere) forest caused mainly by the hemlock woolly adelgid (Adelges tsugae Annand) was detected, quantified, and mapped for a 1,267 km² study area in the New Jersey Highlands using anniversary dates of Landsat Thematic Mapper data (1984 and 1994). A model relating estimates of canopy condition to the temporal difference in near infrared/red reflectance (i.e., the vegetative index difference) was developed to predict and map four classes of hemlock condition across the study area. Data from 105 circular ground plots (90 m diameter) were used to develop the regression model, while data from 50 plots were reserved for accuracy assessment. The vegetative index difference was highly correlated to hemlock damage as measured on the ground (R² = 0.73). Lightly defoliated hemlock canopy did not differ spectrally from healthy hemlock; thus, these two classes were joined together. Accuracy assessment showed that hemlock condition can be predicted within one-half damage class with an overall accuracy of 64% for four damage classes, 70-72% for three classes, and 78-92% for two classes. Of the 7,735 ha of hemlock forest in 1984, 47% remained healthy to lightly defoliated, 44% had experienced moderate to severe defoliation, and 9% were dead by 1994. For. Sci. 43(3):327-335.

Keywords: Adelges tsugae; Tsuga canadensis; image differencing; insect defoliation; remote sensing

Document Type: Journal Article

Affiliations: Associate Professor, Center for Remote Sensing and Spatial Analysis, Department of Ecology, Evolution and Natural Resources, Cook College, Rutgers University, New Brunswick, NJ 08903

Publication date: 1997-08-01

More about this publication?
  • Forest Science is a peer-reviewed journal publishing fundamental and applied research that explores all aspects of natural and social sciences as they apply to the function and management of the forested ecosystems of the world. Topics include silviculture, forest management, biometrics, economics, entomology & pathology, fire & fuels management, forest ecology, genetics & tree improvement, geospatial technologies, harvesting & utilization, landscape ecology, operations research, forest policy, physiology, recreation, social sciences, soils & hydrology, and wildlife management.
    Forest Science is published bimonthly in February, April, June, August, October, and December.

    2015 Impact Factor: 1.702
    Ranking: 16 of 66 in forestry

    Also published by SAF:
    Journal of Forestry
    Other SAF Publications
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